The present invention relates to studded snowmobile tracks and, in particular, to a self-threading retainer having an exposed surface which contains a number of raised, secondary studs which project adjacent a primary stud. The secondary studs enhance track traction and may be used with or without the primary stud. A track engaging surface of the retainer includes a number of raised surfaces disposed adjacent a tapered recess to secure the retainer to a track without squeeze out or tearing.
A variety of studs and threaded stud retainers have been developed for snowmobile tracks. Examples of some early studs, which are attached with rivets and which have multiple, pointed gripping surfaces are shown at U.S. Pat. No. 3,572,851 and Des. Pat. No. 238,764.
A more typical, present day assembly provides a metal stud which includes a threaded shank and a pointed end that is shaped to promote traction and the gripping of a preferred terrain (e.g. snow or ice). Some of these studs provide a shank that mounts through a hole in the track and is fastened to a base plate on the opposite side of the track. Other studs provide an integral flanged base which mounts on the inside of the track and a terrain engaging end that mounts on the outside of the track. A threaded fastener (e.g. a nut and washer or other threaded retainer) mates with a threaded portion of the shank to secure the stud to the track. The exposed tip and edges of the shank can be formed to a preferred gripping shape or a separate formed tip can be attached to the shank. A washer with grip enhancing surfaces might also be secured to the stud shank. Examples of various known stud and retainer constructions are shown at U.S. Pat. Nos. 4,758,055; 5,188,441; 5,234,266; and 5,573,316.
U.S. Pat. No. 5,299,860 also discloses a molded plastic retainer that can be used to secure a threaded stud to a track. The retainer is used with studs having a flanged base and which base includes a hexagon shaped recess which receives an Allen wrench. An exposed surface of the retainer includes a raised hexagon surface which accepts a socket or wrench to facilitate retainer mounting.
Nowhere does the art disclose a retainer having separate gripping surfaces which promote the gripping of a supported stud with the terrain and retention of the retainer to the track. The present invention therefore provides a self-threading molded plastic retainer having spiked or raised, secondary surfaces which enhance gripping of the terrain. A track engaging surface of the retainer also includes a number of projections and recesses which promote the retention of the retainer to the track without damaging the track.